Infectious keratitis in contact lens wearers Infectious keratitis is a sight-threatening complication in contact lens wearers. The infection is most frequently caused by bacteria (Pseudomonas aeruginosa). However, fungi or Acanthamoeba are found in increasing frequency. Three cases illustrate a characteristic course: patient A (11-year-old male) was treated for three weeks before the characteristic aspect of Acanthamoeba keratitis was recognized and confirmed. Patient B (45-year-old female) developed a severe corneal ulcer within 4 days; microbiological diagnostics confirmed Pseudomonas aeruginosa keratitis. Examination of patient C (27-year-old female) showed an infiltrate with satellites, typical of fungal keratitis. It is important to check the use of contact lenses in patients with keratitis. Referral to the ophthalmologist is mandatory: immediate in cases with an infiltrate. A dentritiform epithelial lesion in a contact lens wearer is indicative of Acanthamoeba keratitis, whereas fungal keratitis shows satellites or feathering edges. Steroids may only be prescribed by an ophthalmologist after confirmation of the causative agent.